Now I am pretty sure that a goodly percentage of the Gentle Readers are looking at the title and going, “What???” A significant number will recognize it as a reference to the Constitution, but to be honest only a limited number of people know that Article I defines the Legislative Branch, Article II the Executive, and Article III the Judicial. Most people are not quite sure about the other Articles.
Let’s cut to the chase. It is the Supremacy Clause:
This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.
The reason that states have to obey Federal laws and the Constitution as a whole is specifically because of this clause of the Constitution. That obedience is not optional, conditional, or debatable. If you are part of the United States, you are subject to Federal law and your “feelz” otherwise have no bearing. If you disagree with Federal law, if you want to deny rights under the Constitution, you are out of luck. You can try to change it in court. You can try to have Congress pass a change to the law or repeal it. You can try to amend the Constitution. But the Federal power in the areas where the Constitution grants lawmaking power to the Federal government over-rides anything the States can do.
This is key to the functioning of a free, constitutional republic. If a state, or group of states, can defy the Federal government at will, there is no Federal government. There is no equal justice under the law. And there is, in fact, no rule of law.
This was recognized from the beginning. In Federalist #44 James Madison pointed out that if it was not included, then each state would have functional veto power over the entire country. Without it, the country would not work.
There have been 3 attempts to over-ride or ignore the Supremacy clause and each was aimed at destroying the country.